The chromatography technique is widely used in different forms for separating chemical and biological substances and there are many applications in compound preparation, purification and analysis. Liquid chromatography is of particular importance in the pharmaceutical and biological industries for the preparation, purification and analysis of proteins, peptides and nucleic acids.
A typical liquid chromatography apparatus has an upright housing in which a bed of packing material, which is usually particulate in nature and consists of a porous medium, rests against a permeable retaining layer. A liquid mobile phase enters through an inlet, for example at the end of an adaptor rod which has an elongated extension within the column. The liquid mobile phase thereafter enters a distributor plate which distributes the liquid mobile phase through a porous, perforated filter, mesh, frit or net, which together with the distributor plate is arranged on an adaptor. The liquid mobile phase thereafter moves through the bed of packing material and is finally removed via an outlet, typically through a second filter, mesh, frit or net and a second distributor plate.
Columns used in liquid chromatography typically comprise a tubular body enclosing the porous chromatography medium through which the carrier liquid or mobile phase flows, with separation of substances or analytes taking place between the mobile phase and solid phase of the porous medium. Typically, the porous medium is enclosed in the column as a packed bed, generally formed by consolidating a suspension of discrete particles, known as slurry that is pumped, poured or sucked into the column, usually from a bore or nozzle located at a tubular housing or at one end of the column. The production of a stable, even bed is often critical to the final separation process.
Another critical feature in the separation of substances is the fluid distribution system, particularly as the cross-section of the chromatographic column increases. The efficiency of the chromatographic separation relies on the liquid distribution and collection system at the fluid inlet and outlet of the packed bed. Ideally, the carrier liquid is uniformly introduced throughout the surface at the top of the packing, flows through the packing at the same velocity throughout the packing cross section, and is uniformly removed at the plane defined by the bottom of the packed bed.
Conventional distribution systems for use in liquid chromatography comprise a distributor plate attached to the net. The distributor plate comprises channels arranged in a pattern to substantially uniform distribute the fluid over the plate. The distributor plate is perforated with holes or openings which lead the fluid from the channels and uniformly into the packed bed.
Applying a sample volume simultaneously over the crossectional area of the packed bed is critical for the result of the chromatography process. Un-uniform distribution of the sample volume will lead to increased dispersion in the chromatographic system by broadening the convective residence time distribution of a tracer substance transported with the fluid throughout the system. The dispersion generated by the liquid distribution system has to be controlled in relation to the amount of dispersion introduced by the chromatographic packed bed itself by means of diffusion and mixing effects. Without a simultaneous introduction of fluid in the plane defined by the top of the bed, it is virtually impossible to achieve so-called plug-flow behavior, which is a uniform and well-defined movement of the sample through the packed bed and column, respectively, resulting in a uniform residence time distribution.
During the chromatography process the packed bed may be damaged and fines may occur in the column. After several chromatography cycles the fines may clog the net or nets in the column, which may result in higher back pressure and lower process efficiency. Therefore, the nets must be replaced after a number of cycles.
According to known chromatography columns the nets are welded or heat shrinked on the distributor plate, which distributor plate in turn is removably connected by fastening elements on the adaptor. Time and cost consuming operations are necessary in order to remove the clogged net from the distributor plate. Especially, when the chromatography column is of a large size the removal of the net from the distributor plate by using milling or turning machines is complicated. The replaced net must be welded or heat shrinked on the distributor plate before remounting on the adaptor. The chromatography column may not be used under a substantially period of time during the replacement of the nets. This may lead to production losses in the pharmaceutical and biological industries.
Also, compression fluid held within the column above the adaptor must be drained from the column before replacing the filter on the adaptor. Draining the column of compression fluid is time consuming and requires special equipment.
Document WO2010/132011A1 discloses a chromatography column provided with an adaptor, a filter and a distributor plate. Notwithstanding the existence of such prior art, there is a need to improve the maintenance methods available for chromatography columns by providing columns which are safer and easier for operators to use. Also, there is a need to reduce cost and time when conducting maintenance on chromatography columns. Also, there is a need to reduce complexity and to reduce needed floor space when conducting maintenance on chromatography columns. There is also a need for an improved and more efficient filter that is easy, fast and safe to replace. Because the filter is in contact with fluid used in a chemical process it is also important that the filter is easy to clean.